Journal of the Japan Institute of Metals and Materials
Online ISSN : 1880-6880
Print ISSN : 0021-4876
ISSN-L : 0021-4876
Volume 55, Issue 8
Displaying 1-11 of 11 articles from this issue
  • Eiichi Sato, Kazuhiko Kuribayashi, Ryo Horiuchi
    1991 Volume 55 Issue 8 Pages 839-847
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Deformation induced grain growth is usually observed during structural superplasticity. This paper proposes a new deformation model explaining this grain growth based on grain switching proposed by Ashby and Verrall.
    To begin with, an irregularity of a pentagon-heptagon pair is introduced into a two-dimensional grain structure constructed with a regular hexagonal array. This irregularity geometrically corresponds to an edge dislocation of the grain structure. The tensile stress oblique to the pair results the grain switching described by dislocation glide. On the other hand, the stress parallel to it results the grain switching which transforms the pentagon into the quadrilateral and then removes it. It can be described by dislocation climb and results the enhancement of grain growth. Therefore superplastic deformation (grain switching) induces grain growth due to the strain.
    In order to extend this model to three dimensions, an edge dislocation is introduced into a three-dimensional grain structure constructed with Kelvin’s tetra-kai-dekahedra (14-faced grains). The grain at the tip of the half grain plane is 13-faced or 11-faced. A 17-faced or 15-faced grain is contacting it, respectively. Since these coincide with the pentagon-hexagon pair in two dimensions, the above discussion in two dimensions can use in three dimensions with little modifications.
    This model predicts the grain growth rate equation as
    (This article is not displayable. Please see full text pdf.)
    \ oindentThis well agrees with the experimental results in dual phase structure.
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  • Hajime Goto, Yoichi Nishino, Shigeru Asano
    1991 Volume 55 Issue 8 Pages 848-852
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Internal friction in polycrystalline copper varying grain size was measured as a function of strain amplitude at around 700 Hz by means of the free decay method of flexual vibration. The curves of the amplitude dependence are found to shift to higher amplitude with decreasing grain size. The data are analyzed on the basis of the phenomenological theory of microplasticity and converted into typical mechanical responses such as the microplastic strain expressed as a function of stress. The microplastic flow stress increases with decreasing grain size in a similar way to macroplastic deformation. However, the variation of microplastic flow stress with grain size is much greater than that of macroplastic flow stress. The flow stress at the plastic strain of 1×10−9 cannot be expressed by the Hall-Petch relation, a simple linear function of the inverse square root of grain size, and is almost constant when grain size is larger than 80 μm. This means that the constraining force of an individual grain by surrounding ones markedly decreases in coarse-grained specimens under the influence of surfaces. As the plastic strain increases, however, the microplastic flow stress appeares to approach the Hall-Petch relation.
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  • Katsutoshi Matsumoto, Shoji Taniguchi, Atsushi Kikuchi
    1991 Volume 55 Issue 8 Pages 853-859
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Experimental and theoretical studies on the initial leaching rate of a spherical pellet of ZnO in HA (A = ClO4, NO3, Cl), HA-ZnA2 and HA-NaA solution have been made to discuss the characteristics of liquid phase mass transfer for ZnO-acid solution systems in an agitated vessel.
    The results obtained are as follows:
    (1) For the ZnO-HA systems, the leaching rate is proportional to the concentration of acid and 0.6 power of stirring rate, and also is the same for three different acids.
    (2) For the ZnO-HA-ZnA2 systems, the rate is same for three different acids and increases with concentration of ZnA2. At high concentration of ZnA2, however, the rate is different for each acid.
    (3) For the ZnO-HA-NaA systems, the rate is the same for three different acids, and increases with NaA concentration.
    (4) The results of dissolution rate of benzoic acid into aqueous solution and leaching rate for the ZnO-HA systems show that the leaching process for the systems studied is controlled by the liquid phase mass transfer.
    (5) The rates calculated by a mass-transfer model based on a film theory involving diffusion and electrical migration are consistent with the experimental ones for the ZnO-HA, ZnO-HA-NaA and ZnO-HA-Zn (ClO4)2 systems.
    For the ZnO-HA-Zn(NO3)2 and the ZnO-HA-ZnCl2 systems, the calculated values are not consistent with the experimental ones at a high concentration of ZnA2, although the model gives good agreement between the two values at a low concentration of ZnA2.
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  • Nagayasu Bessho, Shoji Taniguchi, Atsushi Kikuch
    1991 Volume 55 Issue 8 Pages 860-866
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The rates of decarburization of liquid iron by CO2-CO gas mixtures were measured to discuss the mass-transfer characteristics in the gas phase for a system of reaction between an impinging jet of gas and liquid iron stirred inductively in a crucible under various conditions (concentration of carbon in liquid iron ≥0.2 mass%, gas flow rate=(0.83∼4.17)×10−5 m3 NTP·s−1, mol fraction of CO2=0.1∼1.0, diameter of nozzle=(0.66∼1.32)×10−2 m, temperature=1773∼1973 K, and frequency of furnace = 9.0, 480.0 kHz.).
    Results obtained are as follows:
    (1) The decarburization rates under the above experimental conditions depend upon factors such as the gas flow rate, the concentration of CO2 in gas phase and the nozzle diameter which affect the gas-phase mass transfer. While the rates are affected hardly by the temperature which affects the chemical reaction, and also are independent of the concentration of carbon in liquid iron and the frequency of furnace which affect the mass-transfer rate in liquid. From these, it is shown that the decarburization is controlled by the mass transfer in the gas phase.
    (2) Sherwood numbers Sh(=kGdDAB) obtained from observed values of rates and a rate equation of the gas-phase mass transfer are correlated by an equation,
    (This article is not displayable. Please see full text pdf.)
    \ oindentwhere kG is the mass transfer coefficient for gas phase, d the diameter of nozzle, DAB the diffusion coefficient, rs, the radius of crucible, v the kinematic viscosity of gas, and uG the velocity of gas in nozzle.
    (3) The Sherwood numbers Sh obtained from reported values of decarburization rates are roughly consistent with those given by the above empirical equation.
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  • Masakazu Niinae, Atsuhiro Oboso, Yuka Takenaka, Yoshitaka Nakahiro, Ta ...
    1991 Volume 55 Issue 8 Pages 867-873
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    As a part of the fundamental studies on the recovery of Au by solvent extraction, the synergistic effect of combined extractants on the extraction of Au from sulfuric acid solution containing thiourea was investigated.
    Extractants tested were di-(2-ethylhexyl) phosphoric acid (D2EHPA), tri-n-octylamine (TOA), tri-n-butyl phosphate (TBP) and trioctyl phosphine oxide (TOPO). Four kinds of extractant combinations, D2EHPA/TBP, D2EHPA/TOPO, TOA/TBP and TOA/TOPO, were testsd to clarify the synergistic effect on the extraction of Au in terms of various concentration ratios, diluents, the concentration of sulfuric acid and the concentration of thiourea.
    The results obtained in this study were summarized as follows:
    (1) Combined extractants were superior to D2EHPA and TOA on the extraction of Au, the separation of Au and Fe (III) and the phase separation behavior.
    (2) D2EHPA/TOPO and TOA/TOPO were favorable to the extraction of Au and the separation of Au and Fe (III), respectively, compared with D2EHPA/TBP and TOA/TBP.
    (3) Benzene used as diluent was favorable to the extraction of Au and the separation of Au and Fe (III).
    (4) The extraction efficiency of Au and the separation efficiency of Au and Fe (III) were not dependent on the concentration of thiourea, but the concentration of sulfuric acid.
    (5) The mechanisms of the extraction of Au with the combined extractants were discussed.
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  • Kiyoshi Mizuuchi, Yoshihira Okanda, Itsuo Ohnaka
    1991 Volume 55 Issue 8 Pages 874-880
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The rotating-water-atomization process was applied to produce rapidly solidified Fe-30Cr-5Al alloy powders. The size distribution and the mean particle diameter decreased with increasing water-layer velocity. The particle shape was not spherical but tear-drop like. The oxidation of the particle surface was increased with the addition of Ce and also with increasing water-layer velocity. However, in the case of atomizing in Ar atmosphere, the oxidation could be decreased to less than one-half of that in Ar atmosphere. The obtained structure of the as-atomized particles was quite fine and became much finer with the addition of the Ce. A little grain growth by annealing was observed. It is suggested that the ductility of this alloy is improved by rapid quenching and the corrosion resistance against molten salt of this alloy by rapid quenching is as good as that of the as-cast condition.
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  • Tetsuo Yano, Masafumi Yoneda, Akihiro Utsumi, Jun Matsuda, Munehide Ka ...
    1991 Volume 55 Issue 8 Pages 881-886
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Surface hardening behavior of BN coated commercially pure titanium was investigated after laser irradiation or the vacuum-heating. BN film was coated on c.p. titanium by using a dynamic mixing method. After that, CO2 laser beam was irradiated on the specimens for various times up to 40 s. Vacuum-heating was performed on the specimens at 1173 K for various time. The Ti-B-N solid solution phase containing precipitates of TiB and Ti2N was formed by CO2 laser irradiation and vacuum-heating. The surface hardness of the heated specimens was 35∼40 GPa. The surface of the specimens was smooth and had no cracks.
    The influence of the composition and the thickness of the B-N film on the surface hardening behavior was also investigated. The B-coated c.p. titanium in either case of the laser irradiation or the vacuum-heating had the smaller hardness and many surface cracks. The surface hardening behavior of BN2-coated c.p. titanium induced by vacuum-heating was similar to that of BN coated one.
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  • Masatomo Kamada, Youichi Tokunaga
    1991 Volume 55 Issue 8 Pages 887-892
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    The relationship between sintering shrinkage and phase constitution was investigated for (δ/γ ) two phase stainless steel compacts made of equilibrium powders. The chemical compositions of the δ and γ powders were controlled to Fe-27 mass%Cr-7 mass%Ni and Fe-20 mass%Cr-12 mass%Ni, respectively, which were equilibrium compositions at 1473 K, in order to suppress the chemical diffusion of atoms between the powders.
    The sintering shrinkage rate of the compacts increases with an increase in the amount of δ powder owing to the high self-diffusivity of atoms in δ phase. There are some differences in shrinkage rate, however, between the experimental results and the value calculated in proportion to the volume fraction of each phase.
    In compacts containing small volume of δ powder, the experimental shrinkage becomes smaller than the calculated value, because the sintering is controlled by the diffusion of atoms in γ phase. On the other hands, the experimental shrinkage of the compacts containing large volume fraction of δ becomes larger than the calculated value, because the sintering depends upon the diffusion of atoms in δ phase.
    Significant grain growth occurs in δ single phase compacts and this prevents the transgranular pores disappearing during the final stage of sintering. since the grains grow slightly in (δ/γ) two phase compacts, the (δ/γ) compacts containing large volume of δ shrink larger than δ single phase compacts with incerasing sintering time.
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  • Hiroyuki Kon, Yasutoshi Noda, Yoshitaka Furukawa, Isao Nishida, Katash ...
    1991 Volume 55 Issue 8 Pages 893-897
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    Mg2Si0.6Ge0.4 solid solution semiconductor was prepared by direct melting, where the reaction between samples and graphite crucible was suppressed using NaCl flux. Carrier concentrations were controlled in the regions of 6.5×1024∼1.5×1026 electrons/m3 and 1.0×1024∼5.5×1025 holes/m3 by doping Sb and Ag, respectively. Thermal conductivity k was measured at 300 K for Sb-doped samples. By calculating the electronic thermal conductivity kel based on the Fermi integrailon, the lattice thermal conductivity kph was estimated to be 2.10 Wm−1K−1. Figure-of-merits Z, of Mg2Si0.6Ge0.4 at 300 K were 0.69×10−3 K−1 for the n-type sample with an electron concentration of 5.4×1025 m−3 (3000 ppm Sb) and 0.47×10−3 K−1 for p-type one with a hole concentration of 5.2×1025 m−3 (16000 ppm Ag).
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  • Shozaburo Nakashima, Kunihide Takashima, Jirou Harase
    1991 Volume 55 Issue 8 Pages 898-906
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
    A study has been made on the effect of the final thickness, 0.60-0.18 mm, under the same reduction rate in cold rolling on the secondary recrystallization of the grain-oriented electrical steel produced by the single-stage cold rolling process.
    (1) On the heating period of final annealing in the case of the atmosphere of H2, 0.60 mm thick specimen undergoes perfect secondary recrystallization, but specimens thinner than 0.60 mm undergo imperfect secondary recrystallization. The thinner the specimen is, the more part of it is occupied by fine grains. This phenomenon is considered to be attributed to the decrease in MnS and AlN content, i.e., the decline of the effect of inhibition leads to the normal growth of matrix grains in the center part of the thickness on the heating period of final annealing in case of thin specimens.
    (2) On the heating period of final annealing in the case of the atmosphere of the mixture of H2 and N2, all specimens undergo perfect secondary recrystallization. In this case, the thinner the specimen is, the lower the magnetic flux density becomes. This phenomenon is considered to be attributed to the increase in AlN content, i.e., the enrichment of inhibitors which is supposed to cause the increase of the deviation from Goss orientation in the secondary texture in case of thin specimens.
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  • Hideki Takagi, Yutaka Takahashi, Tadatomo Suga, Yoshio Bando
    1991 Volume 55 Issue 8 Pages 907-908
    Published: 1991
    Released on J-STAGE: April 04, 2008
    JOURNAL FREE ACCESS
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